1. Field of the Invention
This invention relates in general to oil and gas well production, and in particular to a system for removing accumulated liquid from gas producing wells.
2. Description of the Prior Art
Many gas wells product both gas and liquids such as water, oil and condensate. The gas is often flowed from the casing to a sales line. Part of the liquid, initially entrained as droplets in the gas flow, drops out of the flow because of insufficient velocity of gas. The liquid accumulates in the bottom of the well, and as accumulation increases, exerts an increasingly large back pressure on the formation. This back pressure, which equals the hydrostatic head of the liquid column, may be large enough to reduce the production rate or completely stop production.
It is therefore advantageous to periodically remove accumulated liquid from gas wells. A typical gas well has casing through which the gas flows through the perforations at the gas producing formation to a production or sales line at the surface or well head. Tubing inside the casing is used to remove accumulated liquids. The tubing usually has an open lower end extending close to the producing formation and into the accumulated liquid. Normally, the tubing is closed by the valve at the surface, and the casing is opened to permit gas to flow into the sales line. Accumulated liquid rises in the casing and in the tubing to the same level. To remove liquid the valve at the top of the tubing is opened to reduce the pressure inside the tubing to a value less than the pressure inside the casing and in the sales line. Thus, the pressure of the gas inside the casing forces liquid through the tubing toward the well head. The liquid and gas from the tubing is discharged into a low pressure storage and disposal system.
In the above method, liquid removal is facilitated by use of a loose fitting plunger which separates the liquid and the gas. This helps prevent the gas from migrating through the liquid and prevents the liquid from dropping through the gas.
There are a number of variations of the above described methods. Two such variations may be seen in U.S. Pat. Nos. 3,053,188 and 3,203,351. One disadvantage of such systems is that they require a second pipe system on the surface leading to the lower pressure storage or disposal facility. This represents a considerable additional amount of pipe and equipment that must be installed and maintained. Also, the gas discharged in the lower pressure system may not be usable unless pressurized to the sales line pressure, which may not be economical.